In the watch and more particularly the wristwatch field, arranging certain elements of the watch such as the movement, the dial or the bezel in a support ring often called the casing ring, which is inserted in the middle part of the watch, is known, as described for example in Swiss Patent No. 681 127.
In the case of a water resistant watch, inserting a plurality of sealing gaskets made of elastomeric material in the vicinity of the back cover, around the stem and watch crystal is known.
Although the machining operations inside the middle part are simplified by the insertion of the casing ring, difficulties remain which have never been satisfactorily resolved. In particular, in order to prevent any angular displacement between the casing ring and the middle part, the latter must, in the prior art, be provided with one or more holes receiving as many catches of the support part or screws in the case of the aforecited document. The problem of the inner dimensions of the middle part, which have to be fitted to the casing ring, thus remains intact.
This problem is particularly acute when the middle part is made of hard materials, for example ceramic materials or hard metal. On the one hand, such parts are generally manufactured by moulding and sintering, thus undergoing dimensional variations which do not allow precise final dimensions to be obtained from the unworked parts. On the other hand, inner machining of these hard parts is very difficult and expensive. In addition to the problem of fitting the casing ring inside the middle part, there is the problem of proper positioning of the ring and thus the clockwork movement, in particular the centring thereof, with respect to a middle part whose unworked or even final dimensions are imprecise.
Elastically suspending the movement in a watch case by means of an elastic ring made of rubber placed between the middle part and an inner metal ring intended to support the movement is known, in particular from French Patent No. 898 248. The rubber ring is pre-manufactured with predetermined dimensions, then inserted in the middle part, to which it is fixed using an adhesive material. It can thus be assembled to the ring by adhesion. This ring rests against the bezel and the back cover of the case to assure sealing and further includes a tubular lateral extension which acts as sealing gasket for the winding stem. However, a ring of this type having predetermined dimensions does not allow variations in the dimensions of the middle part to be compensated, or only very locally. Further, such compensation is not provided in the aforecited Patent.